dh_javadoc: command not found

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH
/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin

If it's empty, You may set the PATH variable with this command

export PATH="/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin"

On Debian possible default full paths are:

/usr/bin/dh_javadoc - from package: gcj-jdk

You may install the required package with command apt-get install {package}

Error in other languages:
dh_javadoc: bevel nie gevind nie
dh_javadoc: comandă negăsită
dh_javadoc: comando não encontrado
dh_javadoc: commande introuvable
dh_javadoc: command not found
dh_javadoc: käsku ei ole
dh_javadoc: không tìm thấy lệnh
dh_javadoc: komanda nerasta
dh_javadoc: Kommando nicht gefunden.
dh_javadoc: kommandot finns inte
dh_javadoc: komut yok
dh_javadoc: nie znaleziono polecenia
dh_javadoc: níor aimsíodh an t-ordú
dh_javadoc: no se encontró la orden
dh_javadoc: no s'ha trobat l'ordre
dh_javadoc: opdracht niet gevonden
dh_javadoc: parancs nem található
dh_javadoc: perintah tidak ditemukan
dh_javadoc: príkaz nenájdený
dh_javadoc: příkaz nenalezen
dh_javadoc: команда не найдена
dh_javadoc: командата не е открита
dh_javadoc: 命令找不到
dh_javadoc: コマンドが見つかりません